McCain, despite being diagnosed with an aggressive form of brain cancer in July 2017, remained a vocal critic of U.S. foreign policy and national security under the Trump administration with his outspoken opposition to Gina Haspel's nomination to lead the CIA and his support of tougher sanctions against Russia.

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The former senator didn’t mention Trump in his farewell statement released Monday, but he appeared to take a parting shot at the ideological differences that have decided the two men for years.

"We weaken our greatness when we confuse our patriotism with tribal rivalries that have sown resentment and hatred and violence in all the corners of the globe,” McCain said in a statement released by his Senate office. “We weaken it when we hide behind walls, rather than tear them down, when we doubt the power of our ideals, rather than trust them to be the great force for change they have always been.”

His death raises fresh questions about who among the Senate Republican Conference will be willing to criticize the administration on foreign affairs, particularly as so many GOP senators have been wary of a direct confrontation with Trump.

"You had two prominent GOP senators say, well, if he wants to get rid of the A.G., we'll help him get a new one, but let's wait until after the midterms,” Schiff said on CNN. “I was proud to see Ben Sasse take issue with that. That was very John McCain–like. We need people like John McCain now more than ever."

But Sasse has come under criticism from both Republicans and Democrats for being seen as unwilling to push back against the administration beyond a tweet or a statement. Washington Post columnist Jennifer Rubin questioned how many times Sasse would "tweet something provocative and then do absolutely nothing to challenge the administration."

The dearth of Trump critics within the Senate Republican Conference isn’t expected to reverse course.

Flake told reporters on Monday that he was concerned it would be harder to find Republicans to push back on Trump’s foreign policy, and he used a Senate floor speech to urge his colleagues to mirror McCain.

“We have lately wasted a lot of words in this town doing and being everything that John McCain was not,” Flake said on the Senate floor. “We would do well to allow this moment to affect us in ways reflected not merely in our words, but in our deeds.”

McCain, Corker and Flake represented the three GOP senators most willing to publicly call out Trump for his rhetoric, especially his warm tone toward Russian President Vladimir Putin and his questioning of decades-old alliances like NATO.

The death of McCain and retirement of Corker, in particular, could represent a seismic shift in how willing congressional Republicans are to act as a check on the Trump White House. McCain served as chairman of the Senate Armed Services Committee.

Both Inhofe and Risch are considered to be more closely aligned with Trump than McCain or Corker, and less likely to use the megaphone their committee perches provide to criticize or attempt to rein in the White House.

“If his death could cause us all to reflect on the way the Senate used to be and try to honor his legacy by not trying to constantly score partisan political points but rather work together for the good of the country, I can think of no finer legacy for John McCain,” she told a Maine radio station.

“We can honor him by trying to carry out the principles he lived by. We can try, as he did, to put country before party. We can try, as he always did, to speak truth to power,” Schumer said. “And we can try … to restore the Senate to its rightful place in our national political life.”